This paper gives a brief review of the currently accepted understanding of sonic boom phenomena and describes the manner in which modified linearized theory and geometric acoustics are used to predict the sonic boom caused by a complex aircraft configuration. Minimization methods that have-evolved in recent years are discussed, with particular attention given to a method developed by Seebass and George for an isothermal atmosphere which was modified for the real atmosphere by Darden. An additional modification which permits the relaxation of the nose bluntness requirement in the defining aircraft also is discussed. Finally, an overview of current areas of sonic boom research is given. I. Introduction T HE ban of supersonic flight over the continental U. S. and the associated economic penalties played a major role in the demise of our national SST program a few years ago. With the impending scheduled flights of the Concorde and then the TU144, the position of the United States in the worldwide aeronautical community is threatened. The sonic boom, which was the primary cause of the ban on supersonic flight over the continental U. S., has undergone considerable investigation by scientists and engineers alike within the past two decades. The ultimate goal of this research has been to develop an understanding of how sonic booms are generated, to develop methods of predicting sonic booms, and, finally, to develop means of reducing the sonic boom so that overland supersonic flight will be made possible. Today, knowledge of sonic boom phenomena is quite advanced and the theoretical methods that have been developed for predicting the sonic boom are generally accepted as giving valid results at flight altitudes for Mach numbers up to about 3. Attention in recent years has been given to ways of reducing the sonic boom by using the existing knowledge of how it is generated. This paper will review the currently accepted understanding of sonic boom phenomena, will outline prediction theories and minimization methods that have evolved in recent years, will discuss drag penalties and tradeoffs associated with low boom configurations, and will mention areas of current research.
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